Added SH_Widget_Animate in QStyle

Added SH_Widget_Animate in QStyle styleHint, and use it to determine
whether widgets should be animated or not.

In this patch QTabBar, QColumnView,QTreeView and QWidgetAnimator are
patched to obey the new Hint.

Change-Id: Iefdbddc52c7843f6653dbfb5462125942489b4d9
Reviewed-by: Olivier Goffart <ogoffart@woboq.com>
Doc: Added \qtvariable command to QDoc.

Specifies the QT variable needed in the .pro file.
The argument of the command is the qmake QT variable.

To use, add "\qtvariable <value>" to a QDoc comment
which contains the \module command.
QDoc will then associate the class with the QT variable.

Only supported for C++ classes at the moment.
Part of work done for QTBUG-32172

Task-number: QTBUG-32172
Change-Id: Ia8eea30fcfc771191c23a5f5994a48732959ea49
Reviewed-by: Martin Smith <martin.smith@digia.com>
Doc: Setting module pages' \qtvariable.

Argument to \qtvariable is the QT variable needed for linking to the
module.

Task-number: QTBUG-32172
Change-Id: I181c0cfaf9529f3aea741cdaee0f20d6cd0e2d2f
Reviewed-by: Martin Smith <martin.smith@digia.com>